Stroke is the leading cause of disability in the United States of America. This is partly because patients have difficulty acquiring, or re-learning old skills. Enhanced skill acquisition could reduce the problem of re- learning old skills, and so reduce the rate of disability. When Transcranial Magnetic Stimulation (TMS) is applied to the primary motor cortex (M1) the rate of subsequent skill learning can be increased in normal individuals. This intervention modulates the encoding or acquisition of a new skill, and produces significant but small and short lived enhancements in skill acquisition. It may be possible to achieve larger and longer lasting improvements by using TMS to modulate procedural consolidation. This process occurs following skill acquisition, and is responsible for the between session skill improvements that normally occur overnight. These "off-line" improvements are usually sleep-dependent. Recently we have been able to induce similar improvements over the day by applying TMS to M1 following skill acquisition. These improvements are substantial and can be detected twelve hours after applying TMS. They are associated exclusively with applying TMS to the ipsilateral M1: there are no off-line improvements following contralateral stimulation. This proposal seeks to establish how long these improvements take to develop and whether it is stimulation to the ipsilateral or to the non-dominant hemisphere that is critical for these improvements. Answering each of these questions will give mechanistic insight into how these improvements are achieved; and will allow skill enhancements induced by TMS to be optimised.